For the sixth time this summer, a high school football player has collapsed and died after practicing in scorching heat.

Al Smith Jr., a 15-year-old sophomore, fell ill and then fainted Tuesday during his second day of practice with the junior varsity team at Eisenhower High School in Houston. He was rushed to the hospital and died two days later.

While Smith's cause of death has not yet been determined, his case bears striking similarities to the deaths of several other high school players this summer.

All six of the deaths have occurred in the heat-stricken South, and all of the players were enduring one of their first practices of the season. Smith also was heavy-set, as were many of the other players who died.

"He was just a good kid, that's all I can say, a good kid," Smith's father, Al Smith Sr., told ABC station KTRK-TV in Houston. "Whatever happened, I'm lost for words."

This tragic football preseason also has claimed the life of an assistant football coach.

Wade McLain, 55, died during the first day of practice at Prestonwood Academy in Plano, Texas, on Aug. 1. He had a heart condition, and was conducting practice in 100-degree heat.

The dangers of student-athletes training in extreme heat create tragedies every year. But this appears to be the most lethal summer for young football players since 1972, when seven players died of heart-related causes, according records compiled by the National Center for Catastrophic Sport Injury Research. Perhaps not-so-coincidentally, this also has been a summer of record-shattering heat.

From 1980 to 1984, an average of one high school football player died each year during the summer practice season. But the death rate has roughly tripled to 2.8 deaths per since then, according to a study last month by the Union of Concerned Scientists.

The researchers concluded that two trends -- the growing number of overweight and obese players and the increasing frequency of heat waves -- are "increasing the risk of heat-related illness and death for high school football players."

The study also found that many deaths occur at the start of the practice season, which it said was most likely the result of young players trying to do too much, too soon.

The first death this summer occurred July 26. Isaiah Laurencin, a 285-pound senior offensive lineman at Miramar High School in South Florida, went into cardiac arrest during his team's second workout session that day.

A gifted player who had three college scholarship offers, Laurencin died a short time later. Autopsy results are pending.

Four days later, Tyquan Brantley, 14, a freshman at Lamar High School in South Carolina, collapsed during practice and later died. The coroner said his death was related to a "sickle-cell crisis" brought on by 101-degree heat.

Two 16-year-old football players in Georgia died on Aug. 2 from heat exhaustion. Donteria Searcy was found unconscious in his cabin after a morning workout at his high school's football camp. Forrest Jones of Locust Grove High School, had passed out after a drill a week earlier, and never regained consciousness.

And in Arkansas, 15-year-old Montel Williams collapsed while wearing full gear an hour into practice at Gurdon High School near Arkadelphia on Aug. 9. The temperature in the area was 93, with a heat index of 110. An autopsy found Williams had a heart condition.